We are studying the structure and function of extracellular matrix components. Molecular approaches have been used to probe the structure of certain molecules and well as to charactrize active domains. In vitro studies have been used to understand the molecular interactions involved in matrix assembly. Our data define how the collagens, proteoglycans and glycoproteins interact with each other to form supramolecular complexes which ultimately assemble to form the mature matrix. Such interactions are important in determining the final structure and function of tissues and likely play an important role during tissue morphogenesis, in wound repair and in pathological states. Various biological activiies of epithelial cells are controlled by basement membrane components. Using three-dimensional cell culture, striking effects on cell growth and differentiation have been observed with basement membrane components. Hair follicles from embryonic mice are found to differentiate and produce a hair shaft while Sertoli cells become 15-fold more columnar and germ cell survival and differentiation are enhanced. The Sertoli cells reform tube like structures when grown inside the three-dimensional matrix. Nerve cell sprouting and growth are significantly improved in vitro and in vivo when a basement membrane gel is placed in contact with the neurons. These and other studies with cultured cells ad organs indicate that matrix components may regulate tissue formation by promoting cell growth and differentiation.